Rollover crash tests are commonly used in the development of rollover detection sensors, algorithms and occupant protection systems. As in many other crash tests, partial damage or complete destruction of the vehicle is not uncommon. The building of new vehicle prototypes alone is a costly endeavor which requires engineers to attempt to maximize the amount of data and analysis gained from a limited number of crash tests available.
Due to the limited availability of destructive crash tests, a majority of the tests used to develop current rollover detection algorithms and occupant protection systems are laboratory based. Safety engineers and researchers have sought to develop component level testing methods that replicate key aspects of a crash test in a repeatable and non-destructive manner. Laboratory based rollover tests often utilize a mechanism, such as sliding a vehicle into a curb or placing the vehicle on a cart and decelerating the cart, to induce vehicle roll. For tripped rollover tests, the key phase events of which the occupant compartment is involved are: the vehicle lateral velocity phase, the tripping or transition to rotation phase, the free flight rotation phase, and the ground impact or landing phase.
Conventional testing attempts to simulate or replicate a few of the key phases of a given crash test. “Spit Test” type devices are capable of generating the free flight motion often seen in the airborne phase of a rollover test. The Dynamic Rollover Fixture and the Rollover Restraint Tester were developed by NHTSA and are examples of these types of devices. “Spit Test” type devices that are capable of generating the free flight motion often seen in the airborne phase of a rollover. The driving force for these devices is provided by a drop tower and free-weight system. The angular velocity ranges from 180°/s to 290°/s and is generated by various combinations of drop weight and drop height. However, it focuses only on the rotational motion occurring during the free flight phase of a typical rollover crash test.
Another conventional testing device which does not include all of the key phases was developed by Breed. This device includes only a portion of the occupant compartment and simulates a quarter turn roll with no free flight motion. The fixture is accelerated using a HYGE™ sled to reach the desired lateral velocity, and the “compartment” is pushed outward by hydraulic pistons at the bottom, causing the compartment fixture to rotation clockwise about the pivot at the top of the compartment fixture allowing the dummy to experience a vehicle rotation. However, this device fails to simulate the occupant compartment free flight or landing phases.
Another conventional testing device attributed to Pywell et al. simulates different quasi-static vehicle rollover conditions for characterizing various belt restraint systems in terms of dummy's excursion. This device can generally achieve a peak roll rate from 240°/s to 360°/s with a rotation up to 180°. However, it fails to simulate the occupant compartment flight phase or the landing phase.
To date, most of the methods used in rollover tests and reported in the literature are either dynamic or quasi-static tests that involve rotating or “inverting” an occupant around a stationary axis. Many have been successful in simulating the rotational phase of a rollover test. However, they fail to take a vehicle's lateral translational motion into consideration. These methods primarily have been used for occupant motion studies, restraint system evaluation and development. Since most vehicle laboratory based rollover events utilize a tripping mechanism that generates lateral vehicle motion, the aforementioned methods fail to adequately characterize the transition of the occupant compartment from lateral to rotational vehicle motion. Additionally, the effects of ground contact are either not simulated or done in a very simplistically manner.
Therefore, a new component rollover test device and methodology is needed. A repeatable, reusable and representative component level testing which incorporates all of the key phases could potentially be instrumental in developing robust occupant restraint systems, rollover detection sensors and understanding occupant kinematics during rollovers.